The present invention relates to the cleaning of surfaces, such as the surfaces of ovens, which are subject to heat and are liable to soiling by baked-on organic food deposits. The soiling matter deposited on these surfaces consists of a complex mixture of natural fats and other organic deposits from the cooking of food. When heated at normal oven temperatures, this soiling matter is converted into a polymeric mass in which part of the organic material may also be carbonized.
The removal of this type of soil is a considerable problem, especially in restaurants where ovens are used to cook large amounts of food and the resulting soil levels are high. Removal of badly burned soils requires the use of highly alkaline, unsafe oven cleaners (typically based on sodium or potassium hydroxide) and/or laborious scrubbing and scraping. The time and effort involved are such a significant deterrent to regular cleaning, for example, on a daily basis, that restaurant ovens are often chronically soiled.
However, the most important disadvantage of these known products is the serious hazard to the eyes and skin arising from the use of caustic alkalis. It is a common practice for users to wear rubber gloves when applying a product of this type to avoid damage to the skin. Such products may also damage adjacent surfaces, such as paint, aluminum or wood, onto which they may be inadvertently applied.
Oven cleaners containing alkali materials less alkaline than caustic soda are known. For example, U.S. Pat. No. 3,658,711, issued April 25, 1972 to Mukai et al., and British Pat. No. 1,275,740 published May 24, 1972 disclose the use of alkali metal phosphates combined with an amine component or "enhancing agent" and other optional ingredients such as, for example, surfactants, abrasives, thickening agents or suspending agents. However, such oven cleaners are not very effective in saponifying baked-on fat in a relatively short period of time and, consequently, are not efficient oven cleaners. Further, such products, when applied to soiled oven surfaces, must attack the soiling matter from the outer surface, while the most severe polymerization and carbonization are generally present in the interior of the soil layer, adjacent to the oven wall.
In contrast to oven cleaners, oven pre-treatment compositions which are applied to oven surfaces prior to further soiling and then removed after further soiling are also known. For instance, U.S. Pat. No. 4,214,915, issued July 29, 1980 to Dillarstone et al., and U.S. Pat. Nos. 3,827,983 and 3,672,993, issued August 6, 1974 and June 27, 1972, respectively, to Mitchell et al., disclose the use of alkali metal bicarbonates, which Mitchell et al. suggests may be heated to decompose to the corresponding, more alkaline carbonates. However, when representative amounts of bicarbonates are heated at typical oven temperatures, the resulting dried films are pock-marked, fragile and, thus, easily damaged by scuffing or chipping when the oven is in use. Further, because the dried film does not remain continuous during the drying step, subsequent deposits of fats and other food soils burn onto the oven surface left exposed while the oven is in use.
It is evident that there is a need in the oven cleaning art for a pre-treatment composition which can be applied to an oven interior, preferably a cleaned oven interior, to produce an alkaline, food-safe coating which is continuous and adheres to all portions of oven surfaces, which remains continuous as the coating dries, preferably by heating, and which also forms a dried durable film, resistant to scuffing or chipping at typical oven heating temperatures, to prevent fats and other food soils from burning onto exposed oven surfaces. After soiling, the film and the accompanying spattered food soils should be quickly and easily removable, preferably by water alone or an aqueous solution.